Rhino 曲线就像是一根线，可以被拉直或弯曲，也可以把两头系紧（闭合）或解开（开放）。
A polycurve is several curve segments joined together end to end.
Rhino 提供多种绘制曲线的工具，您可以绘制平直的直线、由多条直线相连而成的多重直线、圆弧、圆、多边形、椭圆、弹簧线和螺旋线等。
You can also draw curves using curve control points and draw curves that pass through selected points.
请参考: 维基百科: 曲线。
直线是一条没有弯曲的 1 阶曲线，多重直线是由一系列直线或圆弧组合在一起构成的。
Draw a single line segment.
Fit a line through any combination of points, control points, and point-cloud objects.
Draw a multi-segment polyline with options for line and arc segments, tracking line helpers, and close.
Draw a polygon with a specified number of sides with options for inscribed/circumscribed, by edge, star-shaped, around a curve, and vertical.
Draw a rectangular closed polyline from with options for starting at the center, three points, vertical, and rounded with arc or conic corners.
请参考: 维基百科: 直线。
自由造型曲线在 Rhino 是 NURBS 曲线，NURBS 曲线是按照一定的规则，由一组有权重的控制点和节点向量产生。
Rhino 提供了各种各样创建自由造型曲线的方法。
Draw a curve from control point locations.
通过控制杆绘制贝塞尔曲线。
Fit a curve through picked locations.
建立一条通过曲面上指定点的曲线。
Drag the mouse to draw a curve.
请参考: 维基百科: 非有理 B 样条线。
圆锥曲线的定义如下: 用一个平面去截一个圆锥面，得到的相交曲线就是圆锥曲线。平面与圆锥面相交角度不同，得到的曲线也不同，有可能是圆弧、椭圆、抛物线或双曲线。圆弧是圆上的一部分。RhinoAn arc is a part of a circle. 可以通过特定的 Rhino 指令绘制特定的圆锥曲线或通过 Conic 指令绘制自由造型的圆锥曲线，圆锥曲线为 2 阶曲线。
Draw a conic section curve with options for the start, end, apex, and rho value.
Draw an arc with options for center, start, angle, and direction.
Draw a circle from center and radius, diameter, points on the circumference, and circumference length.
Draw a closed elliptical curve from focus points, center and edges, bounding rectangle, and around a curve.
通过焦点、顶点或系数绘制一条双曲线。
通过焦点、顶点或终点绘制一条抛物线。
请参考: 维基百科: 圆锥曲线。
螺旋线是曲线不断增大或缩小与平面上固定的中心点的距离并围绕其旋转产生的曲线。
弹簧线是曲线围绕中心轴以和轴之间固定或连续变化的距离不断旋转产生的曲线。
Draw a helical curve with options for number of turns, pitch, vertical, reverse, and around a curve.
Draw a spiral curve with options for number of turns, pitch, flat, vertical, and around a curve.
请参考: 维基百科: Spiral。
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